NO. 2086. 



SOME MAMMALS OF THE PLEISTOCENE— HAY . 



559 



indices amount to about 10 per cent of the mean. The face is on an 

 average considerably shorter than that of any others of the Equidae 

 here considered ; but cases occur in which it is about as long as that 

 of any of the others. This shows that it is not safe to trust wholly 

 to any single character in determining species. The vomerine notch 

 is nearer the foramen magnum than to the palate in the specimen 

 considered, but the difference is sometimes small. In consideration of 

 the fact that those species which are represented by a considerable 

 number of skulls usually show much less variation than do those 

 of the domestic ass, is it not allowable to suppose that the wide varia- 

 tions of the latter are due to domestication ? 



The materials which have been used in constructing the following 

 table have been found in the schedule of measurements and indices 

 of sixty skulls of Equidae furnished by Nehring in the work already 

 referred to. Besides skulls referred to Equus caballas, Nehring con- 

 sidered the asses and the zebras. The skulls of his list are arranged 

 in the order of their basilar length, beginning with the lowest. From 

 this list the present writer has selected eight skulls near the begin- 

 ning and eight from near the end of it, thus getting a group of small 

 horses and another of large ones. 



Measurements in millimeters and indices of domestic horses. 



Numbers of speci- 

 mens in Nehring's 

 list. 



Basilar 

 length. 



Vertex 

 length. 



Frontal 

 width. 



Ce- 

 phalic 

 index. 



Cranial 

 length. 



Cranio- 



cephalic 



index. 



Facial 

 length. 



Facio- 



cephalic 



index. 



For. 

 mag. to 

 vomer. 



Vomer 



to 

 palate. 



13 



426 



438 

 438 

 443 

 448 

 450 

 450 

 452 



464 

 490 

 492 

 490 

 492 

 490 

 494 

 500 



190 

 201 

 201 

 193 

 202 

 189 

 192 

 201 



44.3 

 45.9 

 45.9 

 43.5 

 45.1 

 42.0 

 42.7 

 44.5 



151 

 162 

 158 

 162 

 163 

 158 

 159 

 162 



35.5 

 36.9 

 36.1 

 36.6 

 36.4 

 35.1 

 35.3 

 35.8 



320 

 327 

 342 

 333 

 357 

 343 

 337 

 337 



75.1 

 74.6 

 78.1 

 75.2 

 79.8 

 76.2 

 74.9 

 74.5 



Ill 

 119 

 107 

 111 

 119 

 109 

 114 

 109 



92 



14 



89 



15 



97 



16 



99 



18 



93 



20 



100 



21 



95 



23 



100 







49 



536 

 542 

 546 

 550 

 558 

 571 

 574 

 585 



584 

 569 

 587 

 586 

 605 

 615 

 623 

 628 



222 

 222 

 216 

 214 

 231 

 236 

 238 

 255 



41.4 

 41.0 

 39.5 

 38.9 

 41.4 

 41.3 

 41.4 

 43.6 



190 

 182 

 168 

 176 

 182 

 183 

 191 

 201 



35.4 

 33.6 

 30.8 

 32.0 

 32.6 

 32.1 

 33.3 

 34.4 



396 

 391 

 419 

 410 

 419 

 414 

 434 

 423 



73.9 

 72.1 

 76.7 

 74.5 

 75.1 

 72.5 

 75.6 

 72.3 



142 

 142 

 136 

 143 

 139 

 141 

 145 

 155 



111 



50 



114 



51 



120 



52 



117 



55 



116 



56 



119 



57 



122 



58 



121 







Averages 



500 



544 



213 



42.7 



172 



34.5 



375 



75.1 



128 



107 



If we now accept all these skulls as belonging to a single species, 

 Equus caballus, we have one which exhibits a very wide range in 

 size and structure. The difference between the basilar length of the 

 smallest and that of the largest skull amounts to 159 mm., nearly 

 32 per cent of the mean length. The difference between the least 

 frontal width and the greatest is 66 mm., more than 30 per cent of 

 the mean frontal width. The cranial length has a range of 50 mm., 

 which is 29 per cent of the mean length; the facial length, a range 



